Sewage Treatment Plant Upgrade

By the time this project began, the island’s existing sewage treatment plant was no longer operating consistently, increasing the risk of discharge to the Marine Park and placing growing pressure on local operators.

Against this backdrop, Premise, now part of the Amey Group, delivered optioneering - the structured assessment of treatment options - followed by concept and detailed design for a new Membrane Bioreactor (MBR) sewage treatment plant, providing a more reliable and sustainable wastewater system for the island.

At a glanceAs part of the project, Premise, now part of the Amey Group, replaced a failing Rotating Biological Contactor plant with a new Membrane Bioreactor (MBR) facilityTo maintain continuous power in a diesel-reliant network, the design integrated solar, wind and 600 kWh battery storage, achieving N+1 resilience To address water quality and environmental risks, the plant incorporates treatment for per- and polyfluoroalkyl substances (PFAS), often referred to as “forever chemicals”, alongside reverse osmosis and effluent reuse The system is supported by automated control through SCADA (Supervisory Control and Data Acquisition)The challenge What challenges arise when operating a failing sewage treatment system on a remote island?

As the condition of the Norfolk Island plant declined, the wastewater system came under increasing pressure as demand and environmental expectations increased. There was little tolerance for disruption, and any interruption would carry immediate consequences for essential services and the surrounding marine environment.

Maintaining operations became increasingly difficult. Local teams were required to manage faults and outages with limited access to specialist support, increasing operational pressure and response times.

This was compounded by a set of practical constraints that shaped how any solution could be delivered:

An ageing Rotating Biological Contactor plant, providing limited treatment

A remote island location and corrosive marine environment, requiring all materials to be shipped from mainland Australia

A site located close to the airport runway, with strict Civil Aviation Safety Authority (CASA) height constraints

A diesel-powered electricity network, where outages risk interrupting continuous treatment

Limited access to specialist operators, placing reliance on a small local workforce

High PFAS concentrations in influent, requiring on-island treatment as off-island disposal was not viable